Personally, it *seems* to me to be:

Slave Pens (stun Soothsayers, Champions, Rays, Greater Bogstrok, in that order)
Botanica (stun robots, Menders, the blood elf with each pack of dragonhawks, Harvesters, the white fear-causing mutate things)
Mechanar (stun robots, physicians, wreckers, crushers, and in the fight right before the boss - the netherbinder [MC])
Underbog (stun the non-blue small plant guys in groups, the rays near the end, spearmen [drain mana])
(Haven't found any others I really like yet, haven't tried boxing most others though.)

*IF* when the first mob gets to your tank you stun it, I've found that things go SO much better. My team is dishing out so much dps these days it isn't as big of a deal now, but when I was first doing heroics it was huge to me. Learning which mob to stun really helps too.

You guys think SV is easy? Even though the first boss has two lightning storms? How do you avoid those from wiping your group?